that should theoretically work. the rear end might have a larger tracking on the 4G then 3G, but should still fit regardless, but I'd keep the 3G rear leafs personally. if you upgrade the front to 4G, you'd need 4G wheels as well, I think.Yep, it was almost exactly like the beginning of your quest into good brakes. lol
I have to find the 4th gen rear axle, and probably re plumb the rusted lines to the back and get a new master. I think the fronts will be fine for now.
I wouldn't mind upgrading the rear brakes on my PT to discs but not in a huge hurry because the brakes on it work good enough. Never hit them hard enough to get them to even squeak, its not like I haven't tried before either lol.